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DTSTART:20260308T070000
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DTSTART:20261101T060000
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DTSTART;TZID=America/Toronto:20261124T163000
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URL:https://uwaterloo.ca/combinatorics-and-optimization/events/cryptography
 -seminar-rolfe-schmidt-making-signal-protocol
SUMMARY:Cryptography Seminar | Rolfe Schmidt\, Making the Signal Protocol\n
 Quantum Safe: Where We Are and What’s Next
CLASS:PUBLIC
DESCRIPTION:SPEAKER:\n Rolfe Schmidt\n\nAFFILIATION:\n Signal\n\nLOCATION:\
 n United College\, Room 105\n\nABSTRACT: In 2023 Signal deployed PQXDH\,
  a small change to the\nhandshake that protects new conversations against 
 adversaries who\nrecord traffic today and decrypt it with a future quantum
  computer.\nTwo gaps remain: post-compromise security in the ratchet and\n
 authentication in the handshake both still rely on elliptic curves.\nThis 
 talk describes how we closed the first and how we plan to close\nthe secon
 d.\n\nIn the first part\, we look at the challenge of building a post-quan
 tum\nratcheted messaging protocol in a bandwidth-constrained setting\, and
 \nbuild up Signal’s Sparse Post-Quantum Ratchet\, deployed in 2025\,\nst
 ep by step through a series of simpler protocols.\n\nIn the second part\, 
 we look ahead to a new handshake that completes\nthe transition of Signal
 ’s 1:1 messaging with hybrid\, deniable\nauthentication. While the post-
 quantum ratchet feels like an\nengineering variation on the classical one\
 , the post-quantum key\nagreement takes a very different shape. Our need t
 o save bandwidth\nstill drives plenty of engineering\, including Merkle tr
 ees\, Falcon\nsignature recovery modes\, and context-specific optimization
 s.\n\nI’ll close with open questions and a brief look at what it will ta
 ke\nto make the rest of the Signal app quantum safe.
DTSTAMP:20261113T210029Z
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